Building Components and Construction Methods
Domain 2 tests Building Components and Construction Methods: naming the part of a building, its position in the vertical sequence, and the order in which site operations are carried out.
Components from bottom to top
- Foundation: shallow types are spread (wall) footing, isolated, combined and raft; deep foundations are piles. It transfers load to soil below the safe bearing capacity.
- Plinth: the portion between ground level and floor level; plinth height keeps the floor above damp and drainage.
- DPC: damp-proof course, 40–50 mm of cement mortar 1:2 with waterproofing compound, or a bitumen membrane, laid continuously at plinth level under walls.
- Walls: load-bearing (brick or stone) or non-load-bearing infill in a framed structure.
- Lintel over openings, with a chhajja (sunshade) projecting outside; slab or roof above; parapet around the roof; sill and threshold at openings.
- Staircase: tread, riser, nosing, waist slab, landing.
Method sequence
Excavation → levelling and laying the plain cement concrete bed → foundation masonry → plinth and DPC → superstructure masonry with lintels → roof slab → plaster, flooring and finishing. Formwork props under a slab are normally kept about 7 days (14 days for beams and longer spans).
Worked example
A new room shows damp patches at the bottom of the walls after the monsoon. Reasoning: moisture rises by capillary action from the soil. The remedy is a continuous DPC at plinth level, lapped with the floor layer and not broken at door openings where a sill is provided.
Traps
- Calling a lintel a beam; a beam is a structural member carrying load, a lintel carries masonry over an opening.
- Placing the DPC above plinth level or leaving gaps under door frames.
- Writing curing as 24 hours instead of 7 days for ordinary Portland cement concrete.